1. Field of the Invention
The present invention relates to a new and improved gladhand security lock apparatus and particularly a better bolt mechanism for such an apparatus.
2. Description of Related Art
In the trucking industry, tractors and trailers can be interchanged as modular units. A fleet of tractor cabs and a fleet of tractor trailers can be used interchangeably. To facilitate interchangability, the hitches for the tractors and trailers are standardized. Tractor trailers are generally compatible with most trailers. Loaded trailers are vulnerable to unauthorized tractor drivers hitching their tractors to the trailer and taking possession of the trailer with its valuable contents. This presents a security problem for the trucking industry.
As a result, devices have been invented to discourage theft of tractor trailers. Some devices prevent theft by denying access to trailer brake line couplings called gladhands.
Tractor trailers employ an air brake system having a coupling mechanism known as a gladhand. The gladhands are employed to couple air pressure from the tractor to the brake line of the trailer to be towed.
When the gladhand is disconnected from the cab air line, air pressure is released thus locking the trailer brakes. The wheels cannot be unlocked unless a brake hose coupling is attached to the gladhand. Various locking mechanisms have been proposed to lock trailer gladhands against coupling to an unauthorized tractor.
The contents of the trailers are often valuable enough to render the trailers a continued target of persistent, sophisticated thieves. If a locking device embodies a weakness in only one aspect of its design, the whole device is limited. Locking devices need therefore be more than a superficial deterrent.
U.S. Pat. No. 4,226,103 shows a gladhand locking device which is brought into engagement with the gladhand from a diametrical direction. Once engaged, a locking pin is urged down into a central air passage opening of the gladhand to maintain the engagement. The effectiveness of the locking device is dependant upon the inner diameter of the air passage and subjects the inner wall of such air passage to damage. It cannot be used with gladhands having a screen across the air passage opening or with those incorporating a spider blocking access thereto from a radial direction.
U.S. Pat. No. 4,325,237 describes a lock plug for a gladhand brake line coupler. The lock plug inserts into the air passage opening and its effectiveness is therefore limited to only those devices having compatible internal dimensions.
A brake line coupler lock having a post that is inserted into the brake line air passage is shown in U.S. Pat. No. 4,693,096. The post is connected to a metal retaining bracket that has two downwardly disposed arms that wrap around the brake hand. At the extremities of the arms are holes. A lock may be attached through the holes. The lock bar of the '096 device can be cut with a hacksaw, wire cutters, or bolt cutters. The retaining bracket can be cut by heavy-duty metal cutters.
U.S. Pat. No. 5,129,243 assigned to the assignee of the present application shows a sturdy cast iron locking device that is rotatably attached to the gladhand in the same manner that the brake line air coupling from the cab is attached to a gladhand. A shortcoming of this device is that it relies on a plunger which is in practice unfortunately exposed to the point where access can be had thereto by an unauthorized individual so it could be hacksawed into thereby releasing the brake.
It is therefore an object of this invention to make an improved gladhand security lock apparatus the effectiveness of which is not dependant on the size of the gladhand air passage.
It is another object of this invention to make a lock apparatus that can be used with virtually all gladhands and which will deter unauthorized severance of the locking plunger thereby discouraging removal.
Thus it is an object of this invention to make a gladhand lock apparatus using a locking mechanism that is more difficult to pry open or saw through.